1 ================================== 1 ==================================
2 GPIO Descriptor Consumer Interface 2 GPIO Descriptor Consumer Interface
3 ================================== 3 ==================================
4 4
5 This document describes the consumer interface !! 5 This document describes the consumer interface of the GPIO framework. Note that
>> 6 it describes the new descriptor-based interface. For a description of the
>> 7 deprecated integer-based GPIO interface please refer to legacy.rst.
6 8
7 9
8 Guidelines for GPIOs consumers 10 Guidelines for GPIOs consumers
9 ============================== 11 ==============================
10 12
11 Drivers that can't work without standard GPIO 13 Drivers that can't work without standard GPIO calls should have Kconfig entries
12 that depend on GPIOLIB or select GPIOLIB. The 14 that depend on GPIOLIB or select GPIOLIB. The functions that allow a driver to
13 obtain and use GPIOs are available by includin 15 obtain and use GPIOs are available by including the following file::
14 16
15 #include <linux/gpio/consumer.h> 17 #include <linux/gpio/consumer.h>
16 18
17 There are static inline stubs for all function 19 There are static inline stubs for all functions in the header file in the case
18 where GPIOLIB is disabled. When these stubs ar 20 where GPIOLIB is disabled. When these stubs are called they will emit
19 warnings. These stubs are used for two use cas 21 warnings. These stubs are used for two use cases:
20 22
21 - Simple compile coverage with e.g. COMPILE_TE 23 - Simple compile coverage with e.g. COMPILE_TEST - it does not matter that
22 the current platform does not enable or sele 24 the current platform does not enable or select GPIOLIB because we are not
23 going to execute the system anyway. 25 going to execute the system anyway.
24 26
25 - Truly optional GPIOLIB support - where the d 27 - Truly optional GPIOLIB support - where the driver does not really make use
26 of the GPIOs on certain compile-time configu 28 of the GPIOs on certain compile-time configurations for certain systems, but
27 will use it under other compile-time configu 29 will use it under other compile-time configurations. In this case the
28 consumer must make sure not to call into the 30 consumer must make sure not to call into these functions, or the user will
29 be met with console warnings that may be per 31 be met with console warnings that may be perceived as intimidating.
30 Combining truly optional GPIOLIB usage with 32 Combining truly optional GPIOLIB usage with calls to
31 ``[devm_]gpiod_get_optional()`` is a *bad id 33 ``[devm_]gpiod_get_optional()`` is a *bad idea*, and will result in weird
32 error messages. Use the ordinary getter func 34 error messages. Use the ordinary getter functions with optional GPIOLIB:
33 some open coding of error handling should be 35 some open coding of error handling should be expected when you do this.
34 36
35 All the functions that work with the descripto 37 All the functions that work with the descriptor-based GPIO interface are
36 prefixed with ``gpiod_``. The ``gpio_`` prefix 38 prefixed with ``gpiod_``. The ``gpio_`` prefix is used for the legacy
37 interface. No other function in the kernel sho 39 interface. No other function in the kernel should use these prefixes. The use
38 of the legacy functions is strongly discourage 40 of the legacy functions is strongly discouraged, new code should use
39 <linux/gpio/consumer.h> and descriptors exclus 41 <linux/gpio/consumer.h> and descriptors exclusively.
40 42
41 43
42 Obtaining and Disposing GPIOs 44 Obtaining and Disposing GPIOs
43 ============================= 45 =============================
44 46
45 With the descriptor-based interface, GPIOs are 47 With the descriptor-based interface, GPIOs are identified with an opaque,
46 non-forgeable handler that must be obtained th 48 non-forgeable handler that must be obtained through a call to one of the
47 gpiod_get() functions. Like many other kernel 49 gpiod_get() functions. Like many other kernel subsystems, gpiod_get() takes the
48 device that will use the GPIO and the function 50 device that will use the GPIO and the function the requested GPIO is supposed to
49 fulfill:: 51 fulfill::
50 52
51 struct gpio_desc *gpiod_get(struct dev 53 struct gpio_desc *gpiod_get(struct device *dev, const char *con_id,
52 enum gpiod 54 enum gpiod_flags flags)
53 55
54 If a function is implemented by using several 56 If a function is implemented by using several GPIOs together (e.g. a simple LED
55 device that displays digits), an additional in 57 device that displays digits), an additional index argument can be specified::
56 58
57 struct gpio_desc *gpiod_get_index(stru 59 struct gpio_desc *gpiod_get_index(struct device *dev,
58 cons 60 const char *con_id, unsigned int idx,
59 enum 61 enum gpiod_flags flags)
60 62
61 For a more detailed description of the con_id 63 For a more detailed description of the con_id parameter in the DeviceTree case
62 see Documentation/driver-api/gpio/board.rst 64 see Documentation/driver-api/gpio/board.rst
63 65
64 The flags parameter is used to optionally spec 66 The flags parameter is used to optionally specify a direction and initial value
65 for the GPIO. Values can be: 67 for the GPIO. Values can be:
66 68
67 * GPIOD_ASIS or 0 to not initialize the GPIO a 69 * GPIOD_ASIS or 0 to not initialize the GPIO at all. The direction must be set
68 later with one of the dedicated functions. 70 later with one of the dedicated functions.
69 * GPIOD_IN to initialize the GPIO as input. 71 * GPIOD_IN to initialize the GPIO as input.
70 * GPIOD_OUT_LOW to initialize the GPIO as outp 72 * GPIOD_OUT_LOW to initialize the GPIO as output with a value of 0.
71 * GPIOD_OUT_HIGH to initialize the GPIO as out 73 * GPIOD_OUT_HIGH to initialize the GPIO as output with a value of 1.
72 * GPIOD_OUT_LOW_OPEN_DRAIN same as GPIOD_OUT_L 74 * GPIOD_OUT_LOW_OPEN_DRAIN same as GPIOD_OUT_LOW but also enforce the line
73 to be electrically used with open drain. 75 to be electrically used with open drain.
74 * GPIOD_OUT_HIGH_OPEN_DRAIN same as GPIOD_OUT_ 76 * GPIOD_OUT_HIGH_OPEN_DRAIN same as GPIOD_OUT_HIGH but also enforce the line
75 to be electrically used with open drain. 77 to be electrically used with open drain.
76 78
77 Note that the initial value is *logical* and t 79 Note that the initial value is *logical* and the physical line level depends on
78 whether the line is configured active high or 80 whether the line is configured active high or active low (see
79 :ref:`active_low_semantics`). 81 :ref:`active_low_semantics`).
80 82
81 The two last flags are used for use cases wher 83 The two last flags are used for use cases where open drain is mandatory, such
82 as I2C: if the line is not already configured 84 as I2C: if the line is not already configured as open drain in the mappings
83 (see board.rst), then open drain will be enfor 85 (see board.rst), then open drain will be enforced anyway and a warning will be
84 printed that the board configuration needs to 86 printed that the board configuration needs to be updated to match the use case.
85 87
86 Both functions return either a valid GPIO desc 88 Both functions return either a valid GPIO descriptor, or an error code checkable
87 with IS_ERR() (they will never return a NULL p 89 with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned
88 if and only if no GPIO has been assigned to th 90 if and only if no GPIO has been assigned to the device/function/index triplet,
89 other error codes are used for cases where a G 91 other error codes are used for cases where a GPIO has been assigned but an error
90 occurred while trying to acquire it. This is u 92 occurred while trying to acquire it. This is useful to discriminate between mere
91 errors and an absence of GPIO for optional GPI 93 errors and an absence of GPIO for optional GPIO parameters. For the common
92 pattern where a GPIO is optional, the gpiod_ge 94 pattern where a GPIO is optional, the gpiod_get_optional() and
93 gpiod_get_index_optional() functions can be us 95 gpiod_get_index_optional() functions can be used. These functions return NULL
94 instead of -ENOENT if no GPIO has been assigne 96 instead of -ENOENT if no GPIO has been assigned to the requested function::
95 97
96 struct gpio_desc *gpiod_get_optional(s 98 struct gpio_desc *gpiod_get_optional(struct device *dev,
97 c 99 const char *con_id,
98 e 100 enum gpiod_flags flags)
99 101
100 struct gpio_desc *gpiod_get_index_opti 102 struct gpio_desc *gpiod_get_index_optional(struct device *dev,
101 103 const char *con_id,
102 104 unsigned int index,
103 105 enum gpiod_flags flags)
104 106
105 Note that gpio_get*_optional() functions (and 107 Note that gpio_get*_optional() functions (and their managed variants), unlike
106 the rest of gpiolib API, also return NULL when 108 the rest of gpiolib API, also return NULL when gpiolib support is disabled.
107 This is helpful to driver authors, since they 109 This is helpful to driver authors, since they do not need to special case
108 -ENOSYS return codes. System integrators shou 110 -ENOSYS return codes. System integrators should however be careful to enable
109 gpiolib on systems that need it. 111 gpiolib on systems that need it.
110 112
111 For a function using multiple GPIOs all of tho 113 For a function using multiple GPIOs all of those can be obtained with one call::
112 114
113 struct gpio_descs *gpiod_get_array(str 115 struct gpio_descs *gpiod_get_array(struct device *dev,
114 con 116 const char *con_id,
115 enu 117 enum gpiod_flags flags)
116 118
117 This function returns a struct gpio_descs whic 119 This function returns a struct gpio_descs which contains an array of
118 descriptors. It also contains a pointer to a 120 descriptors. It also contains a pointer to a gpiolib private structure which,
119 if passed back to get/set array functions, may 121 if passed back to get/set array functions, may speed up I/O processing::
120 122
121 struct gpio_descs { 123 struct gpio_descs {
122 struct gpio_array *info; 124 struct gpio_array *info;
123 unsigned int ndescs; 125 unsigned int ndescs;
124 struct gpio_desc *desc[]; 126 struct gpio_desc *desc[];
125 } 127 }
126 128
127 The following function returns NULL instead of 129 The following function returns NULL instead of -ENOENT if no GPIOs have been
128 assigned to the requested function:: 130 assigned to the requested function::
129 131
130 struct gpio_descs *gpiod_get_array_opt 132 struct gpio_descs *gpiod_get_array_optional(struct device *dev,
131 133 const char *con_id,
132 134 enum gpiod_flags flags)
133 135
134 Device-managed variants of these functions are 136 Device-managed variants of these functions are also defined::
135 137
136 struct gpio_desc *devm_gpiod_get(struc 138 struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id,
137 enum 139 enum gpiod_flags flags)
138 140
139 struct gpio_desc *devm_gpiod_get_index 141 struct gpio_desc *devm_gpiod_get_index(struct device *dev,
140 142 const char *con_id,
141 143 unsigned int idx,
142 144 enum gpiod_flags flags)
143 145
144 struct gpio_desc *devm_gpiod_get_optio 146 struct gpio_desc *devm_gpiod_get_optional(struct device *dev,
145 147 const char *con_id,
146 148 enum gpiod_flags flags)
147 149
148 struct gpio_desc *devm_gpiod_get_index 150 struct gpio_desc *devm_gpiod_get_index_optional(struct device *dev,
149 151 const char *con_id,
150 152 unsigned int index,
151 153 enum gpiod_flags flags)
152 154
153 struct gpio_descs *devm_gpiod_get_arra 155 struct gpio_descs *devm_gpiod_get_array(struct device *dev,
154 156 const char *con_id,
155 157 enum gpiod_flags flags)
156 158
157 struct gpio_descs *devm_gpiod_get_arra 159 struct gpio_descs *devm_gpiod_get_array_optional(struct device *dev,
158 160 const char *con_id,
159 161 enum gpiod_flags flags)
160 162
161 A GPIO descriptor can be disposed of using the 163 A GPIO descriptor can be disposed of using the gpiod_put() function::
162 164
163 void gpiod_put(struct gpio_desc *desc) 165 void gpiod_put(struct gpio_desc *desc)
164 166
165 For an array of GPIOs this function can be use 167 For an array of GPIOs this function can be used::
166 168
167 void gpiod_put_array(struct gpio_descs 169 void gpiod_put_array(struct gpio_descs *descs)
168 170
169 It is strictly forbidden to use a descriptor a 171 It is strictly forbidden to use a descriptor after calling these functions.
170 It is also not allowed to individually release 172 It is also not allowed to individually release descriptors (using gpiod_put())
171 from an array acquired with gpiod_get_array(). 173 from an array acquired with gpiod_get_array().
172 174
173 The device-managed variants are, unsurprisingl 175 The device-managed variants are, unsurprisingly::
174 176
175 void devm_gpiod_put(struct device *dev 177 void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
176 178
177 void devm_gpiod_put_array(struct devic 179 void devm_gpiod_put_array(struct device *dev, struct gpio_descs *descs)
178 180
179 181
180 Using GPIOs 182 Using GPIOs
181 =========== 183 ===========
182 184
183 Setting Direction 185 Setting Direction
184 ----------------- 186 -----------------
185 The first thing a driver must do with a GPIO i 187 The first thing a driver must do with a GPIO is setting its direction. If no
186 direction-setting flags have been given to gpi 188 direction-setting flags have been given to gpiod_get*(), this is done by
187 invoking one of the gpiod_direction_*() functi 189 invoking one of the gpiod_direction_*() functions::
188 190
189 int gpiod_direction_input(struct gpio_ 191 int gpiod_direction_input(struct gpio_desc *desc)
190 int gpiod_direction_output(struct gpio 192 int gpiod_direction_output(struct gpio_desc *desc, int value)
191 193
192 The return value is zero for success, else a n 194 The return value is zero for success, else a negative errno. It should be
193 checked, since the get/set calls don't return 195 checked, since the get/set calls don't return errors and since misconfiguration
194 is possible. You should normally issue these c 196 is possible. You should normally issue these calls from a task context. However,
195 for spinlock-safe GPIOs it is OK to use them b 197 for spinlock-safe GPIOs it is OK to use them before tasking is enabled, as part
196 of early board setup. 198 of early board setup.
197 199
198 For output GPIOs, the value provided becomes t 200 For output GPIOs, the value provided becomes the initial output value. This
199 helps avoid signal glitching during system sta 201 helps avoid signal glitching during system startup.
200 202
201 A driver can also query the current direction 203 A driver can also query the current direction of a GPIO::
202 204
203 int gpiod_get_direction(const struct g 205 int gpiod_get_direction(const struct gpio_desc *desc)
204 206
205 This function returns 0 for output, 1 for inpu 207 This function returns 0 for output, 1 for input, or an error code in case of error.
206 208
207 Be aware that there is no default direction fo 209 Be aware that there is no default direction for GPIOs. Therefore, **using a GPIO
208 without setting its direction first is illegal 210 without setting its direction first is illegal and will result in undefined
209 behavior!** 211 behavior!**
210 212
211 213
212 Spinlock-Safe GPIO Access 214 Spinlock-Safe GPIO Access
213 ------------------------- 215 -------------------------
214 Most GPIO controllers can be accessed with mem 216 Most GPIO controllers can be accessed with memory read/write instructions. Those
215 don't need to sleep, and can safely be done fr 217 don't need to sleep, and can safely be done from inside hard (non-threaded) IRQ
216 handlers and similar contexts. 218 handlers and similar contexts.
217 219
218 Use the following calls to access GPIOs from a 220 Use the following calls to access GPIOs from an atomic context::
219 221
220 int gpiod_get_value(const struct gpio_ 222 int gpiod_get_value(const struct gpio_desc *desc);
221 void gpiod_set_value(struct gpio_desc 223 void gpiod_set_value(struct gpio_desc *desc, int value);
222 224
223 The values are boolean, zero for inactive, non !! 225 The values are boolean, zero for low, nonzero for high. When reading the value
224 value of an output pin, the value returned sho !! 226 of an output pin, the value returned should be what's seen on the pin. That
225 That won't always match the specified output v !! 227 won't always match the specified output value, because of issues including
226 open-drain signaling and output latencies. 228 open-drain signaling and output latencies.
227 229
228 The get/set calls do not return errors because 230 The get/set calls do not return errors because "invalid GPIO" should have been
229 reported earlier from gpiod_direction_*(). How 231 reported earlier from gpiod_direction_*(). However, note that not all platforms
230 can read the value of output pins; those that 232 can read the value of output pins; those that can't should always return zero.
231 Also, using these calls for GPIOs that can't s 233 Also, using these calls for GPIOs that can't safely be accessed without sleeping
232 (see below) is an error. 234 (see below) is an error.
233 235
234 236
235 GPIO Access That May Sleep 237 GPIO Access That May Sleep
236 -------------------------- 238 --------------------------
237 Some GPIO controllers must be accessed using m 239 Some GPIO controllers must be accessed using message based buses like I2C or
238 SPI. Commands to read or write those GPIO valu 240 SPI. Commands to read or write those GPIO values require waiting to get to the
239 head of a queue to transmit a command and get 241 head of a queue to transmit a command and get its response. This requires
240 sleeping, which can't be done from inside IRQ 242 sleeping, which can't be done from inside IRQ handlers.
241 243
242 Platforms that support this type of GPIO disti 244 Platforms that support this type of GPIO distinguish them from other GPIOs by
243 returning nonzero from this call:: 245 returning nonzero from this call::
244 246
245 int gpiod_cansleep(const struct gpio_d 247 int gpiod_cansleep(const struct gpio_desc *desc)
246 248
247 To access such GPIOs, a different set of acces 249 To access such GPIOs, a different set of accessors is defined::
248 250
249 int gpiod_get_value_cansleep(const str 251 int gpiod_get_value_cansleep(const struct gpio_desc *desc)
250 void gpiod_set_value_cansleep(struct g 252 void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
251 253
252 Accessing such GPIOs requires a context which 254 Accessing such GPIOs requires a context which may sleep, for example a threaded
253 IRQ handler, and those accessors must be used 255 IRQ handler, and those accessors must be used instead of spinlock-safe
254 accessors without the cansleep() name suffix. 256 accessors without the cansleep() name suffix.
255 257
256 Other than the fact that these accessors might 258 Other than the fact that these accessors might sleep, and will work on GPIOs
257 that can't be accessed from hardIRQ handlers, 259 that can't be accessed from hardIRQ handlers, these calls act the same as the
258 spinlock-safe calls. 260 spinlock-safe calls.
259 261
260 262
261 .. _active_low_semantics: 263 .. _active_low_semantics:
262 264
263 The active low and open drain semantics 265 The active low and open drain semantics
264 --------------------------------------- 266 ---------------------------------------
265 As a consumer should not have to care about th 267 As a consumer should not have to care about the physical line level, all of the
266 gpiod_set_value_xxx() or gpiod_set_array_value 268 gpiod_set_value_xxx() or gpiod_set_array_value_xxx() functions operate with
267 the *logical* value. With this they take the a 269 the *logical* value. With this they take the active low property into account.
268 This means that they check whether the GPIO is 270 This means that they check whether the GPIO is configured to be active low,
269 and if so, they manipulate the passed value be 271 and if so, they manipulate the passed value before the physical line level is
270 driven. 272 driven.
271 273
272 The same is applicable for open drain or open 274 The same is applicable for open drain or open source output lines: those do not
273 actively drive their output high (open drain) 275 actively drive their output high (open drain) or low (open source), they just
274 switch their output to a high impedance value. 276 switch their output to a high impedance value. The consumer should not need to
275 care. (For details read about open drain in dr 277 care. (For details read about open drain in driver.rst.)
276 278
277 With this, all the gpiod_set_(array)_value_xxx 279 With this, all the gpiod_set_(array)_value_xxx() functions interpret the
278 parameter "value" as "active" ("1") or "inacti !! 280 parameter "value" as "asserted" ("1") or "de-asserted" ("0"). The physical line
279 level will be driven accordingly. 281 level will be driven accordingly.
280 282
281 As an example, if the active low property for 283 As an example, if the active low property for a dedicated GPIO is set, and the
282 gpiod_set_(array)_value_xxx() passes "active" !! 284 gpiod_set_(array)_value_xxx() passes "asserted" ("1"), the physical line level
283 will be driven low. 285 will be driven low.
284 286
285 To summarize:: 287 To summarize::
286 288
287 Function (example) line prop 289 Function (example) line property physical line
288 gpiod_set_raw_value(desc, 0); don't car 290 gpiod_set_raw_value(desc, 0); don't care low
289 gpiod_set_raw_value(desc, 1); don't car 291 gpiod_set_raw_value(desc, 1); don't care high
290 gpiod_set_value(desc, 0); default ( 292 gpiod_set_value(desc, 0); default (active high) low
291 gpiod_set_value(desc, 1); default ( 293 gpiod_set_value(desc, 1); default (active high) high
292 gpiod_set_value(desc, 0); active lo 294 gpiod_set_value(desc, 0); active low high
293 gpiod_set_value(desc, 1); active lo 295 gpiod_set_value(desc, 1); active low low
294 gpiod_set_value(desc, 0); open drai 296 gpiod_set_value(desc, 0); open drain low
295 gpiod_set_value(desc, 1); open drai 297 gpiod_set_value(desc, 1); open drain high impedance
296 gpiod_set_value(desc, 0); open sour 298 gpiod_set_value(desc, 0); open source high impedance
297 gpiod_set_value(desc, 1); open sour 299 gpiod_set_value(desc, 1); open source high
298 300
299 It is possible to override these semantics usi 301 It is possible to override these semantics using the set_raw/get_raw functions
300 but it should be avoided as much as possible, 302 but it should be avoided as much as possible, especially by system-agnostic drivers
301 which should not need to care about the actual 303 which should not need to care about the actual physical line level and worry about
302 the logical value instead. 304 the logical value instead.
303 305
304 306
305 Accessing raw GPIO values 307 Accessing raw GPIO values
306 ------------------------- 308 -------------------------
307 Consumers exist that need to manage the logica 309 Consumers exist that need to manage the logical state of a GPIO line, i.e. the value
308 their device will actually receive, no matter 310 their device will actually receive, no matter what lies between it and the GPIO
309 line. 311 line.
310 312
311 The following set of calls ignore the active-l 313 The following set of calls ignore the active-low or open drain property of a GPIO and
312 work on the raw line value:: 314 work on the raw line value::
313 315
314 int gpiod_get_raw_value(const struct g 316 int gpiod_get_raw_value(const struct gpio_desc *desc)
315 void gpiod_set_raw_value(struct gpio_d 317 void gpiod_set_raw_value(struct gpio_desc *desc, int value)
316 int gpiod_get_raw_value_cansleep(const 318 int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
317 void gpiod_set_raw_value_cansleep(stru 319 void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value)
318 int gpiod_direction_output_raw(struct 320 int gpiod_direction_output_raw(struct gpio_desc *desc, int value)
319 321
320 The active low state of a GPIO can also be que 322 The active low state of a GPIO can also be queried and toggled using the
321 following calls:: 323 following calls::
322 324
323 int gpiod_is_active_low(const struct g 325 int gpiod_is_active_low(const struct gpio_desc *desc)
324 void gpiod_toggle_active_low(struct gp 326 void gpiod_toggle_active_low(struct gpio_desc *desc)
325 327
326 Note that these functions should only be used 328 Note that these functions should only be used with great moderation; a driver
327 should not have to care about the physical lin 329 should not have to care about the physical line level or open drain semantics.
328 330
329 331
330 Access multiple GPIOs with a single function c 332 Access multiple GPIOs with a single function call
331 ---------------------------------------------- 333 -------------------------------------------------
332 The following functions get or set the values 334 The following functions get or set the values of an array of GPIOs::
333 335
334 int gpiod_get_array_value(unsigned int 336 int gpiod_get_array_value(unsigned int array_size,
335 struct gpio_ 337 struct gpio_desc **desc_array,
336 struct gpio_ 338 struct gpio_array *array_info,
337 unsigned lon 339 unsigned long *value_bitmap);
338 int gpiod_get_raw_array_value(unsigned 340 int gpiod_get_raw_array_value(unsigned int array_size,
339 struct g 341 struct gpio_desc **desc_array,
340 struct g 342 struct gpio_array *array_info,
341 unsigned 343 unsigned long *value_bitmap);
342 int gpiod_get_array_value_cansleep(uns 344 int gpiod_get_array_value_cansleep(unsigned int array_size,
343 str 345 struct gpio_desc **desc_array,
344 str 346 struct gpio_array *array_info,
345 uns 347 unsigned long *value_bitmap);
346 int gpiod_get_raw_array_value_cansleep 348 int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
347 str 349 struct gpio_desc **desc_array,
348 str 350 struct gpio_array *array_info,
349 uns 351 unsigned long *value_bitmap);
350 352
351 int gpiod_set_array_value(unsigned int 353 int gpiod_set_array_value(unsigned int array_size,
352 struct gpio_ 354 struct gpio_desc **desc_array,
353 struct gpio_ 355 struct gpio_array *array_info,
354 unsigned lon 356 unsigned long *value_bitmap)
355 int gpiod_set_raw_array_value(unsigned 357 int gpiod_set_raw_array_value(unsigned int array_size,
356 struct g 358 struct gpio_desc **desc_array,
357 struct g 359 struct gpio_array *array_info,
358 unsigned 360 unsigned long *value_bitmap)
359 int gpiod_set_array_value_cansleep(uns 361 int gpiod_set_array_value_cansleep(unsigned int array_size,
360 str 362 struct gpio_desc **desc_array,
361 str 363 struct gpio_array *array_info,
362 uns 364 unsigned long *value_bitmap)
363 int gpiod_set_raw_array_value_cansleep 365 int gpiod_set_raw_array_value_cansleep(unsigned int array_size,
364 366 struct gpio_desc **desc_array,
365 367 struct gpio_array *array_info,
366 368 unsigned long *value_bitmap)
367 369
368 The array can be an arbitrary set of GPIOs. Th 370 The array can be an arbitrary set of GPIOs. The functions will try to access
369 GPIOs belonging to the same bank or chip simul 371 GPIOs belonging to the same bank or chip simultaneously if supported by the
370 corresponding chip driver. In that case a sign 372 corresponding chip driver. In that case a significantly improved performance
371 can be expected. If simultaneous access is not 373 can be expected. If simultaneous access is not possible the GPIOs will be
372 accessed sequentially. 374 accessed sequentially.
373 375
374 The functions take four arguments: 376 The functions take four arguments:
375 377
376 * array_size - the number of array 378 * array_size - the number of array elements
377 * desc_array - an array of GPIO des 379 * desc_array - an array of GPIO descriptors
378 * array_info - optional information 380 * array_info - optional information obtained from gpiod_get_array()
379 * value_bitmap - a bitmap to store th 381 * value_bitmap - a bitmap to store the GPIOs' values (get) or
380 a bitmap of values to assign to the 382 a bitmap of values to assign to the GPIOs (set)
381 383
382 The descriptor array can be obtained using the 384 The descriptor array can be obtained using the gpiod_get_array() function
383 or one of its variants. If the group of descri 385 or one of its variants. If the group of descriptors returned by that function
384 matches the desired group of GPIOs, those GPIO 386 matches the desired group of GPIOs, those GPIOs can be accessed by simply using
385 the struct gpio_descs returned by gpiod_get_ar 387 the struct gpio_descs returned by gpiod_get_array()::
386 388
387 struct gpio_descs *my_gpio_descs = gpi 389 struct gpio_descs *my_gpio_descs = gpiod_get_array(...);
388 gpiod_set_array_value(my_gpio_descs->n 390 gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc,
389 my_gpio_descs->i 391 my_gpio_descs->info, my_gpio_value_bitmap);
390 392
391 It is also possible to access a completely arb 393 It is also possible to access a completely arbitrary array of descriptors. The
392 descriptors may be obtained using any combinat 394 descriptors may be obtained using any combination of gpiod_get() and
393 gpiod_get_array(). Afterwards the array of des 395 gpiod_get_array(). Afterwards the array of descriptors has to be setup
394 manually before it can be passed to one of the 396 manually before it can be passed to one of the above functions. In that case,
395 array_info should be set to NULL. 397 array_info should be set to NULL.
396 398
397 Note that for optimal performance GPIOs belong 399 Note that for optimal performance GPIOs belonging to the same chip should be
398 contiguous within the array of descriptors. 400 contiguous within the array of descriptors.
399 401
400 Still better performance may be achieved if ar 402 Still better performance may be achieved if array indexes of the descriptors
401 match hardware pin numbers of a single chip. 403 match hardware pin numbers of a single chip. If an array passed to a get/set
402 array function matches the one obtained from g 404 array function matches the one obtained from gpiod_get_array() and array_info
403 associated with the array is also passed, the 405 associated with the array is also passed, the function may take a fast bitmap
404 processing path, passing the value_bitmap argu 406 processing path, passing the value_bitmap argument directly to the respective
405 .get/set_multiple() callback of the chip. Tha 407 .get/set_multiple() callback of the chip. That allows for utilization of GPIO
406 banks as data I/O ports without much loss of p 408 banks as data I/O ports without much loss of performance.
407 409
408 The return value of gpiod_get_array_value() an 410 The return value of gpiod_get_array_value() and its variants is 0 on success
409 or negative on error. Note the difference to g 411 or negative on error. Note the difference to gpiod_get_value(), which returns
410 0 or 1 on success to convey the GPIO value. Wi 412 0 or 1 on success to convey the GPIO value. With the array functions, the GPIO
411 values are stored in value_array rather than p 413 values are stored in value_array rather than passed back as return value.
412 414
413 415
414 GPIOs mapped to IRQs 416 GPIOs mapped to IRQs
415 -------------------- 417 --------------------
416 GPIO lines can quite often be used as IRQs. Yo 418 GPIO lines can quite often be used as IRQs. You can get the IRQ number
417 corresponding to a given GPIO using the follow 419 corresponding to a given GPIO using the following call::
418 420
419 int gpiod_to_irq(const struct gpio_des 421 int gpiod_to_irq(const struct gpio_desc *desc)
420 422
421 It will return an IRQ number, or a negative er 423 It will return an IRQ number, or a negative errno code if the mapping can't be
422 done (most likely because that particular GPIO 424 done (most likely because that particular GPIO cannot be used as IRQ). It is an
423 unchecked error to use a GPIO that wasn't set 425 unchecked error to use a GPIO that wasn't set up as an input using
424 gpiod_direction_input(), or to use an IRQ numb 426 gpiod_direction_input(), or to use an IRQ number that didn't originally come
425 from gpiod_to_irq(). gpiod_to_irq() is not all 427 from gpiod_to_irq(). gpiod_to_irq() is not allowed to sleep.
426 428
427 Non-error values returned from gpiod_to_irq() 429 Non-error values returned from gpiod_to_irq() can be passed to request_irq() or
428 free_irq(). They will often be stored into IRQ 430 free_irq(). They will often be stored into IRQ resources for platform devices,
429 by the board-specific initialization code. Not 431 by the board-specific initialization code. Note that IRQ trigger options are
430 part of the IRQ interface, e.g. IRQF_TRIGGER_F 432 part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup
431 capabilities. 433 capabilities.
432 434
433 435
434 GPIOs and ACPI 436 GPIOs and ACPI
435 ============== 437 ==============
436 438
437 On ACPI systems, GPIOs are described by GpioIo 439 On ACPI systems, GPIOs are described by GpioIo()/GpioInt() resources listed by
438 the _CRS configuration objects of devices. Th 440 the _CRS configuration objects of devices. Those resources do not provide
439 connection IDs (names) for GPIOs, so it is nec 441 connection IDs (names) for GPIOs, so it is necessary to use an additional
440 mechanism for this purpose. 442 mechanism for this purpose.
441 443
442 Systems compliant with ACPI 5.1 or newer may p 444 Systems compliant with ACPI 5.1 or newer may provide a _DSD configuration object
443 which, among other things, may be used to prov 445 which, among other things, may be used to provide connection IDs for specific
444 GPIOs described by the GpioIo()/GpioInt() reso 446 GPIOs described by the GpioIo()/GpioInt() resources in _CRS. If that is the
445 case, it will be handled by the GPIO subsystem 447 case, it will be handled by the GPIO subsystem automatically. However, if the
446 _DSD is not present, the mappings between Gpio 448 _DSD is not present, the mappings between GpioIo()/GpioInt() resources and GPIO
447 connection IDs need to be provided by device d 449 connection IDs need to be provided by device drivers.
448 450
449 For details refer to Documentation/firmware-gu 451 For details refer to Documentation/firmware-guide/acpi/gpio-properties.rst
450 452
451 453
452 Interacting With the Legacy GPIO Subsystem 454 Interacting With the Legacy GPIO Subsystem
453 ========================================== 455 ==========================================
454 Many kernel subsystems and drivers still handl 456 Many kernel subsystems and drivers still handle GPIOs using the legacy
455 integer-based interface. It is strongly recomm 457 integer-based interface. It is strongly recommended to update these to the new
456 gpiod interface. For cases where both interfac 458 gpiod interface. For cases where both interfaces need to be used, the following
457 two functions allow to convert a GPIO descript 459 two functions allow to convert a GPIO descriptor into the GPIO integer namespace
458 and vice-versa:: 460 and vice-versa::
459 461
460 int desc_to_gpio(const struct gpio_des 462 int desc_to_gpio(const struct gpio_desc *desc)
461 struct gpio_desc *gpio_to_desc(unsigne 463 struct gpio_desc *gpio_to_desc(unsigned gpio)
462 464
463 The GPIO number returned by desc_to_gpio() can 465 The GPIO number returned by desc_to_gpio() can safely be used as a parameter of
464 the gpio\_*() functions for as long as the GPI 466 the gpio\_*() functions for as long as the GPIO descriptor `desc` is not freed.
465 All the same, a GPIO number passed to gpio_to_ 467 All the same, a GPIO number passed to gpio_to_desc() must first be properly
466 acquired using e.g. gpio_request_one(), and th 468 acquired using e.g. gpio_request_one(), and the returned GPIO descriptor is only
467 considered valid until that GPIO number is rel 469 considered valid until that GPIO number is released using gpio_free().
468 470
469 Freeing a GPIO obtained by one API with the ot 471 Freeing a GPIO obtained by one API with the other API is forbidden and an
470 unchecked error. 472 unchecked error.
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